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Published on: July 4, 2018
Assessing Pain Using the Variation Coefficient of Pupillary Diameter.
David J Charier1, Daniel Zantour2, Vincent Pichot3
1Department of Anesthesia and Intensive Care Medicine, University Hospital, Saint-Etienne, France; Jean Monnet University Research Team EA 4607, SNA-EPIS, Saint-Etienne, France.
The variation coefficient of pupillary diameter (VCPD) objectively measures pain during labor, correlating more strongly with pain intensity than pupillary diameter changes. This method offers a reliable, objective pain assessment tool for various patient groups.
Area of Science:
- Physiology
- Pain Management
- Ophthalmology
Background:
- Pupillary diameter (PD) fluctuates with sympathetic and parasympathetic nervous system activity.
- Pain intensity is known to influence PD, but objective measurement remains challenging.
- Pupillary fluctuations, distinct from static PD, reflect dynamic autonomic interplay.
Purpose of the Study:
- To correlate pupillary diameter (PD), PD increase during contractions, and the variation coefficient of PD (VCPD) with pain intensity during obstetrical labor using a Numeric Rating Scale (NRS).
- To compare the strength of these correlations.
- To evaluate VCPD as an objective pain assessment tool.
Main Methods:
- Forty patients undergoing obstetrical labor were included.
- 160 simultaneous measurements of NRS pain scores, PD, and VCPD were collected.
- Measurements were taken during and outside of uterine contractions, before and after epidural analgesia.
Main Results:
- VCPD showed a stronger correlation with NRS pain scores (r=0.77) compared to PD increase (r=0.42).
- VCPD demonstrated high predictive ability (0.97) for NRS scores ≥4 during labor.
- VCPD measurements over 10 seconds during contractions correlated better with pain than PD increase.
Conclusions:
- VCPD is a more robust indicator of pain intensity during labor than simple PD changes.
- VCPD offers an objective and easily assessable method for evaluating the antinociception-nociception balance.
- This objective pain assessment holds potential for non-communicative patients and critical care settings.
